Provisions - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other
Disclosure of other provisions [line items]
Provisions for deferred employee compensation	$ 391	$ 422

The amount of provisions for employee benefits. [Refer: Employee benefits expense; Provisions]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 78
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_78_d&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_ProvisionsForEmployeeBenefits
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant